Television receiver



Aug. 14, 1956 N. w. PARKER TELEVISION RECEIVER Filed Aug.I l0, 1953mutua. @35g @WML MMM# ATTX TELEVISION RECEIVER Norman W. Parker, ParkForest, Ill., assignor to Motorola, Inc., IChicago, lll., a corporationof Illinois Application August 10, 1953, Serial No. 373,251

2 Claims. (Cl. 3'15-13) This invention relates to cathode ray tubecircuits and more particularly to an improved circuit for dynamicallycontrolling the convergence and/ or focus of the cathode ray beam orbeams in the image reproducing device of a television receiver. Thecircuit may be used for dynamically controlling the convergence r focusof a plurality of beams in a color television system, or of a singlebeam in a monochrome television system.

It is usual in a present color television receiver to provide a cathoderay image reproducing tube in which, for example, three electron orcathode ray beams are developed, each representing a different primarycolor. These beams are directed to the screen of the cathode ray tube atdifferent selected angles and each beam is scanned over dilerentsegments of the screen, these segments being treated to fluoresce inrespective colors corresponding to the colors represented by the beams.To assure proper registry of the respective beams with the segments ofthe screen, an apertured plate or disc or other means such as agrid-like structure is usually mounted adjacent the screen and facingthe beams. It is important for proper registry that the beams becontrolled to converge in the plane of the apertured plate or gridstructure for all positions of the beams as they are swept across thescreen during the line and iield scanning process of the receiver. Forthis reason, it has been found desirable to provide a dynamicconvergence lcontrol in the receiver which exerts a varying controleffect on the cathode ray beams and maintains the beams converged in theplane of the plate throughout the cornplete cycle of each of the lineand field deflections. A convergence control circuit which produces adynamic convergence control signal varying as a function of the linedeiiection signal is disclosed in copending application, Serial No.281,178, led April 8, 1952, in the name of the present inventor entitledColor Television System and assigned to the present assignee. In thatapplication, an essentially parabolic signal is obtained by coupling aresonant network to the line dellection system of the cathode ray imagereproducing tube. The resonant network is tuned to the frequency of theline deiiection signal and is excited thereby to develop a sine wavewhich, during the line trace intervals has an essentially parabolic waveshape. This signal is then applied to an electrostatic convergencecontrol element in the cathode ray tube and functions as a dynamicconvergence control signal to maintain the beams converged in the planeof the apertured disc throughout the entirety of each line deflectioncycle.

lt is also desirable to develop in the receiver a iield convergencecontrol signal that varies as a function of the field deflection signal,and to utilize this latter control signal to maintain the beams inconvergence throughout each field deflection cycle. Due to the fact thatthe field deflection of the beams is carried on at a much lower rate(for example, at 60 cycles as compared with 15,750 cycles for the linedeflection) it is inappropriate to use tuned circuits for providing thedynamic convergence States Patent C control signal for the eld deection.It is therefore necessary to use a different technique to produce thiscontrol signal in the receiver, and it is a general object of thepresent invention to provide a simple and relatively inexpensive networkfor deriving a dynamic convergence control signal from the iield sweepsystem of a color television receiver and for utilizing this controlsignal to maintain the beams converged in the plane of the apertureddisc throughout each field deection cycle.

Another object of the invention is to provide an improved circuit forderiving a eld dynamic convergence control signal from the eld sweepsystem of a color television receiver which is constructed so that thewave shape of the convergent control signal can be manually adjusted toachieve a desired dynamic convergence control for the cathode ray beamsin the image reproducing device during each cycle of the eld deflectionof such beams.

A more general object of the invention is to provide an improved circuitfor developing a control signal from the low frequency eld sweep systemof a television receiver, which control signal is suitable forcontrolling the focus or convergence of the cathode ray beams in thereproducing device of a color television receiver or for controlling thefocus of the cathode ray beam in the reproducing device of a monochrometelevision receiver, throughout each field deection cycle of such beamor beams.

A feature of the invention is the provision of a simpleresistance-capacity network that transforms the peaked sawtoothed fielddeflection signal developed in the field deflection system of atelevision receiver into a control signal for dynamically controllingthe convergence or focus of the cathode ray beams in the imagereproducing device of the receiver, throughout each eld deflectioncycle.

Another feature of the invention is the provision of an improvedresistance-capacity network for transforming the peaked sawtootheddeection signal developed in the iield sweep system of a televisionreceiver into a control signal with an essentially parabolic wave shapefor dynamic convergence of focus control, and which includes a balancingnetwork for distorting the control signal so as to achieve the exactwave shape desired for satisfactory dynamic convergence control.

The above and other features of the invention which are believed to benew are set forth with particularity in the appended claims. Theinvention itself, however, together with further objects and advantagesthereof, may best be understood by reference to the followingdescription when taken in conjunction with the accompanying drawing inwhich the single gure shows a portion of a color television receiverincorporating the improved iield dynamic convergence control network ofthe present invention.

The circuit shown in the accompanying drawing includes a field sweepsystem 10 and line sweep system 11 of a color television receiver, thesweep systems being coupled in well known manner to the synchronizingsignal separator of the receiver (not shown). Line sweep system 11 iscoupled to the line deflection coils of the dellection elements of theimage reproducing device of the receivers, and the sweep system is alsoconnected to an appropriate line dynamic convergence control signalsource 12 which may be similar to that disclosed in the copendingapplication referred to previously herein. As previously mentioned,source 12 develops a dynamic convergence control signal 13, and thiscontrol signal is applied through a capacitor 16 to the convergencecontrol electrode 14 of a cathode ray image reproducing device 15.Electrode 14 may be of any known construction and is usually in the formof a metal tube that setsfup ani-electrostatic Ecld'vvheu a potentialdifference is established between `the electrode and- Aguns- -1f7, -18and 19.

Reproducing `device may be of any well known form and includes, lforexample, three electron guns L7, 1S` and 1.9; "lllesezgunsdevelop threedistinct cathode ray ibeams within' theireproduoi-ngdevice, and tncdreams are direc-ted 1tofthe uorescent screen 20 of the' Adevice fromdiner-ent angles and through an aperture plate or disc 21 positioned:adjacent the screen. AT)The `cathode Vray beams `fromtheel'cctrorr-guns are scanned over the liucrescent screen Z0 bymeans-.ofthe usualy deection elcments 22' including *field kdeflectionKcoilsiand ilin'c deflectioncoils. As previously noted, it is essentialfor proper registry of the beams *on screen 2t?, that they be maintained `inconvergence"in 'the plane of `disc 211 throughout each lineandE iieldf deflectiony cycle.

The receiver includes a static convergence voltage source '123 whichsuppliesf a static convergence voltage of, tor exemple, 9ll'ciicnf'oitsto the convergence control electrode I4 through a resistor24. The static convergence voltage establishes a potential ditference'between electrodes I4 andthe electron 'guns t7, I8 and 19, and' thisestablishes an 'electrostatic convergence held which is adjusted toconverge the b'eamsat `the plate '2 for the reasons .previouslydescribed. The line dynamic convergencesignal Jfrom source I2 cooperateswith the static convergence `voltage to maintain the desired convergenceof the beams throughout each line deflection cycle. lnacc'ordance withthe present invention, the network to be described applies a seconddynamicl convergence signal to the electrode 14 which functions' inconjunction with the line dynamic convergence signal and static.convergence voltage further to maintain 'the beams in convergencethroughout the entirety of each eld deflection cycle.

Field sweep system I0 lincludes a .final amplifier discharge device 2Swhose anode' is coupled to the `positive terminal B+ through the primarywinding of au output transformer 26. The secondary winding oftransformer 26 is connectedy to the field coils of deflection elementsZ2 of the image reproducing. device `15, one side of the secondarywinding being returned to ground.

The top of the primary winding of transformer 26 is coupled Vto thecontrol electrode of a mixing electron discharge device .28 through acapacitor`29 and a pair of series-connected resistors `30, 31. The topof the secondary winding of transformer 26 is coupled to the junction ofresistors 36 and l31 through a coupling capaci-tor 33 andseries-connected resistors 34, 35 and 36. The junction of resistors and36 is coupled to ground through a capacitor 37, .the junction ofresistors 34 and 35 .iscoupled toground through Aa capacitor 33, thejunction of resistorl andthecontrol electrodel of device 2S is coupledto ground through a capacitor 39, and the junction of resistors 35` and36 -is `connected to ground through `a resistor Resistor 35 has amovable tap thereupon which is connected to the emission electrode ofdischarge device' 28. The anode of discharge device 28 is connectedthrough a load resistor 49 to the positive terminal B+ and is coupled toground through a capacitor 41 and seriesconnected resistor 42. Resistor42 has amovable tap thereon which is connected to the control electrodeof an amplilier `discharge vdevice 43. The cathode of discharge device43 is connected to 'a `positive `potential point on a `potentiometerformedy by a .pair of Aresistors 44, 45 connected betweenthe positive`terminal B+ and ground, resistor 45 being shu'nted by a capacitor 46.The anode of discharge device 43 is' connected to the .positive terminalBf+ through a load resistor 47 andis coupled to theconvergence controlelectrode 14 of device 15I through a couplingcapacitor 48.

The primary winding ofv transformer 26 develops, lin `known manner, apeaked sawtooth wave 50 thercacross louency `of the system,-

'each lfield dllection of' the ibe'arns. 'parabolic signal 56 maybeconveniently controlled by whose frequency corresponds to the lfielddeflection frc- .Rcsistor 30 and capacitor 37 constitute a rstintegrating network which transforms the peaked sav/tooth wave 50 intoan unpeaked sawtooth wave 51. Resistor 31 and capacitor 39 constitute asecond integrating network for transforming the unpeaked sawtoothedwaves 51 into aniessentially parabolic Wave 52 which is applied to thecontrol electrode discharge device 2S.

The secondary winding of transformer 26 develops a peaked sa-Wt-oothWave S3 of the same frequency as peaked sawtooth Wave 50 but of reducedamplitude and out of phase therewith. The resistor 34 and capacitor 38constitute a third integrating network which transforms the peaksaiwtooth wave 5S into an unpeaked sau/tooth wave B4. Sawtooth wave '54is of the same frequency as sawtooth wave 5l but in phase oppositiontherewith.

'the` resistors" 36 yand 4t! yfunction as a potentiometer for reducing'the amplitude/of sawtooth wave 5&1 so that it approximatestheamplitu'deof sawto'o'th wave 54. These sawto'oth Waves combi-'ne 4acrossresistor 35 and adjustment ofthe-movable tap'acros'sthc resistorsupplies a sawtooth wave to the cathodeof device ZB corresponding to themixture of the twol inversely phased waves` 51 and 54. Therefore, bymoving the 4tap across resistor 35, a sawtooth wave may "be derivedhaving a selected amplitude anclcorrespondng `inphase either to wave 51or wave 54. At the same time, 'the Vintegrating'nct'vvorl'r 31, 39applies the essentially parabolic wave' 52' to the control electrode ofdischarge 2S and `this Vlattcrvvave is distorted to any desired degreebythe resultan-t Wave applied to the cathode `of 'the device from themovable tap on resistor 35.

Discharge device 2d produces, therefore, a distorted ampiied parabolic-signalSS and applies that signal to device 43 for further amplificationand phase inversion so that the llatter `deviceapplies an ampli'eddistorted parabolic-signal S6' to the' convergence control electrode 14of device 50. Signal A56 functions as the eld dynamic convergencecontrol signal'for the` receiver.`

The distortion of the dynamic convergence control signal 56applied'torconvergerlce control electrode 1-4 may be controlled by"adjustment of the movable tap on potentiometer 35 to provide' theproper convergence of the cathode ray beams in device A15 throughout theentirety of The amplitude-of the adjustment of th'emovable tap' onresistor 42.

Although 'the lpresent invention has been described in conjunction witha color television receiver as providing a dynamic' convergence controlforthe cathode ray beams iu the reproducing device, 'control signal 56may be applied vtoa focusing electrode;A inthe reproducingdevice of acolorV or 'monochrome "television receiver to provide a dynamic focuscontrol for the beams or beam therein.

The present invention provides, therefore, Aa 'relatively simpleresistance capacity network that uses double integration and a balancingarrangement tov transform the peaked sawtoothe'd field deflection signaldeveloped iu a television receiver into a suitable signal fordynamically controlling' the convergence or "focus of the cathode raybeams or beam in the reproducing device of the receiver.

While a particular embodiment `of the invention has 'been shown anddescribed, mod'ications may be made and `it is intended inthe `appended'claims to cover all such modifications 'as fall within Ythe true spirit'and scope of theinvention.

l. A colortelevision receiverincluding in combination, a cathode rayimage reproducing device having means for developing a plurality ofcathode ray beams therein, 'and' a deflection' system coupledtosai'dimage `reproducing device for controlling the deection of the cathoderay beams and including anA output transformer having a primary windingand asecondary winding, said windings developing a pair of oppositelyphased peaked sawtooth waves, a circuit for controlling the convergenceof the cathode ray beams in the reproducing device including incombination, resistance-capacity circuit means coupled to the primarywinding of said output transformer for producing 'a first unpeakedsawtooth signal in response to one of the peaked sawtooth signals,resistancecapacity circuit means coupled to the secondary winding ofsaid output transformer for producing in response to the other of thepeaked sawtooth signals a second unpeaked sawtooth signal of invertedphase relative to the lirst unpeaked sawtooth signal, yaresistance-capacity network for producing a control signal ofessentially parabolic wave shape in response to the rst unpeakedsawtooth signal, Ian ladjustable circuit for mixing the first and secondunpeaked sawtooth signals to produce a resultant sawtooth signal ofselected amplitude and phase with respect thereto, circuit meansincluding an electron disch-arge device for mixing the resultantsawtooth signal with the control signal to distort the control signal,and means for utilizing the distorted control signal to control theconvergence of the cathode ray beams in the image reproducing device.

2. A color television receiver including in combination, a cathode rayimage reproducing device having means for developing a plurality ofcathode ray beams therein, and a deection system coupled to said imagereproducing device for controlling the deection of the cathode ray beamsincluding an output transformer having primary and secondary windingsadapted to develop oppositely phased peaked sawtooth waves, a circuitfor controlling the convergence of the cathode ray beams including incombination, first and second resistant-capacity networks respectivelycoupled to the primary and secondary windings of the output transformerfor producing respective first and second unpeaked sawtooth signals inresponse to the packed sawtooth waves, a third resistantacapacitynetwork coupled to one of the aforementioned networks for producing -acontrol signal of essentially parabolic Wave shape in response to anunpeaked sawtooth signal, adjustable means for mixing the rst and secondunpeaked sawtooth signals to produce a resultant signal of selectedamplitude and phase with respect thereto, an electron discharge devicecoupled to said adjustable means and to said third resistance-capacitynetwork for combining the resultant signal with the control signal toproduce a control effect, and means coupled to said electron dischargedevice to apply said control eiect to the cathode ray image reproducingdevice for controlling the convergence of the cathode ray beams therein.

References Cited in the ile of this patent UNITED STATES PATENTS2,140,284 Farnsworth Dec. 13, 1938 2,224,587 Bahring Dec. 10, 19402,449,524 Witherby et al Sept. 14, 1948 2,613,333 Bull Oct. 7, 19522,664,521 Schlesinger Dec. 29, 1953 2,672,574 Evans Mar. 16, 19542,672,575 Werenfels Mar. 16, 1954 FOREIGN PATENTS 503,462 Belgium Sept.26, 1952 OTHER REFERENCES Proceedings of the I. R. E., October 1951,pages 1249- 1263, article by Albert W. Friend.

